Work machines for metal bars are known, which work one or more bars at a time, for example to make shaped pieces for the building trade or other type of product. Machines that use metal bars normally have a plurality of containers, mounted and/or made on a feed trolley in which respective bundles of bars are prepared, of different diameter between one container and another, from which the bars to be sent to the machine are picked up on each occasion.
The operation of picking up and extracting the individual bars from the bundle is often very difficult, because the bars, which can even reach lengths of 12 meters and more, are disposed haphazard, entangled and twisted with each other.
From WO2005/080021, in the name of the present Applicant, a feed device is known, comprising a first magnetic means which separates from a bundle a head segment of a plurality of bars and disposes said head segments on a plane raised with respect to the bundle, and a second magnetic means which picks up from the first magnetic means one bar at a time from the plurality of bars and discharges it into a desired release position, in particular into a drawing unit of the work machine, so that the bar can be sent for working.
The containers present on the trolley are substantially triangular in shape, with a progressive reduction in width between the top and the bottom. Therefore, as the bars are gradually picked up, the position of the remaining bars is modified with respect to the axis of the drawing unit, and there is no longer any reciprocal alignment.
It is also known, from the Italian patent application IT-A-UD2006A000096, also in the name of the present Applicant, that in order to facilitate the operations of picking up the metal bars from the bundle, the feed trolley is translated laterally, on each occasion, before the pick-up, so as to position the container containing the bundle of bars with respect to the first magnetic means, according to the level of fullness of the container and the relative position of the bars to be picked up inside the container. In this way, a desired pick-up order of the bars is guaranteed.
Normally, however, the feed trolley must be re-positioned after pick-up, in a substantial condition of alignment, at least with a determinate nominal axis with the axis of the drawing unit for the whole duration of the operation to load the bars, so as to facilitate the complete extraction thereof from the relative bundle.
This aligned positioning of the container with the drawing unit does not always coincide with the loading position of the new bars and, therefore, at the end of the complete extraction of the bars, the trolley must again be translated laterally in order to allow the first magnetic means to begin gripping again according to the established pick-up order.
The first magnetic means must therefore wait for the complete extraction of the bars from the bundle before picking up new bars, both to prevent uncontrolled flexions of the bars during extraction, and also due to the risk of knocking the bars being extracted.
Purpose of the present invention is therefore to achieve a device, and perfect a method, for feeding metal bars which will allow to optimize the feed of the bars, reducing operating times between one load and the next, irrespective of their position in the container from which they are taken, and irrespective of the value of the state of fullness of said container.
The Applicant has devised, tested and embodied the present invention to overcome the shortcomings of the state of the art and to obtain these and other purposes and advantages.